Flat Phono Preamp Based on John's P10 and 2SK389

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
Gold
Posts: 500
Joined: Sat Dec 01, 2007 6:20 pm

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Gold » Tue Jan 12, 2016 12:15 am

Since the preamp can be located far from studio meters I thought it might be nice to add a 'calibration' LED in the preamp box. I have a feeling this is fairly easy for anyone but me. It should light an LED at 0.388VAC or -6dBu.

User avatar
JR.
Posts: 2683
Joined: Sat May 24, 2008 7:21 pm

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Tue Jan 12, 2016 8:50 am

My favorite calibration indicator was one I used in my CX decoder. I used an NPN LTP (differential pair), with a two color (3 lead) LED. Below threshold only the green LED was lit, above threshold only the red, and at threshold give or take a few mV both were lit.

Alternately make something simple with a LM339 comparator . Perhaps 3 LEDs one just below, on at, and one just above threshold bracketing the threshold with a fraction of a dB.

Wayne has a thread with a collection of simple peak detectors.

JR

Bill Wilson
Posts: 15
Joined: Wed Dec 08, 2010 11:45 am

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Bill Wilson » Mon Jun 18, 2018 10:23 pm

Hi Wayne: Thought I would jump in with my two cents. I designed my own moving coil phono preamp, using either That 1510 or AD SSM2019 mike pres.
for the balanced input. I based the design around Denons 103R M/C cartridge. The preamp gain is set for 1000 times; as the output from the 103R is 280 micro volts, followed by passive EQ & an adjustable gain output. There are two output impedances; mid unbalanced & fully balanced using a That 1640.

The power supply features our clean power module; providing pure DC +- 15vdc. Sounds great & will be available commercially with my super headphone amplifier.

User avatar
mediatechnology
Posts: 3656
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 9:02 am

Thanks Bill.

I tried the THAT1512 and at DL-103 levels and impedance it was pretty good.

Does the "R" in DL-103R mean re-tipped?
Are the DL-103Rs from cartridge bodies returned to Denon?
I've been wanting to get an "R" since they're reasonably priced.

Is this the preamp/PCB you were working on with Joe?
https://ka-electronics.com

SOCIAL MEDIA PLATFORMS should advance FREEDOM OF SPEECH. Yet too many Americans have seen their accounts suspended, banned, or fraudulently reported for unclear “violations” of user policies.
No matter your views, if you suspect political bias caused such an action to be taken against you, share your story with President Trump.

White House Tech Censorship Reporting Link: https://whitehouse.typeform.com/to/Jti9QH

Bill Wilson
Posts: 15
Joined: Wed Dec 08, 2010 11:45 am

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Bill Wilson » Wed Jun 20, 2018 5:21 pm

Yes Wayne it is the Preamp that Joe Neil did the pcb layout. The 103R is not retipped it is a slightly better cartridge. Some of the users that use mike xfmrs. for stepup claim it is as good as any in the up to $1000- range. I had talked to an applications engr. at That & designed a low Z resistive network
in front of the 150/SSM2019. This avoids the preamp input seeing the 40 ohms direct from the cartridge. I also bought an Audio Technica AT-MONO3/LP
MC Mono cartridge direct from Japan; as they are not sold in the U.S.

User avatar
mediatechnology
Posts: 3656
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 5:47 pm

OK, I was confused the DL-103 is the lower-cost one.
I guess "R" means "reference" :lol:
https://ka-electronics.com

SOCIAL MEDIA PLATFORMS should advance FREEDOM OF SPEECH. Yet too many Americans have seen their accounts suspended, banned, or fraudulently reported for unclear “violations” of user policies.
No matter your views, if you suspect political bias caused such an action to be taken against you, share your story with President Trump.

White House Tech Censorship Reporting Link: https://whitehouse.typeform.com/to/Jti9QH

billshurv
Posts: 245
Joined: Thu Feb 01, 2018 7:07 am

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by billshurv » Wed Jun 20, 2018 6:40 pm

The Denon namings over the years are very confusing. There are/were at least 8 factory variants and, as it's become the flathead V8 of the cartridge world there are a whole slew of retip options effectively off the shelf. It is quite astounding the longevity of this. Still not at VW Beetle levels, but been in continuous production longer than the 2CV was!

Odd guy here has just bought a DL-107, which is a little known MM they made at the same time for the same broadcast client. What I can't justify but want is the DL-107A which was designed to be a plug in replacement for the DL-103. MM with 0.35mV output!

User avatar
mediatechnology
Posts: 3656
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 6:46 pm

billshurv wrote:
Wed Jun 20, 2018 6:40 pm
Still not at VW Beetle levels, but been in continuous production longer than the 2CV was!
I know what a 2CV is. I owned an ID19B.
Bill Wilson wrote:I had talked to an applications engr. at That & designed a low Z resistive network in front of the 150/SSM2019. This avoids the preamp input seeing the 40 ohms direct from the cartridge.
Why? Did it oscillate without it?
https://ka-electronics.com

SOCIAL MEDIA PLATFORMS should advance FREEDOM OF SPEECH. Yet too many Americans have seen their accounts suspended, banned, or fraudulently reported for unclear “violations” of user policies.
No matter your views, if you suspect political bias caused such an action to be taken against you, share your story with President Trump.

White House Tech Censorship Reporting Link: https://whitehouse.typeform.com/to/Jti9QH

Bill Wilson
Posts: 15
Joined: Wed Dec 08, 2010 11:45 am

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Bill Wilson » Tue Mar 05, 2019 7:16 am

No Wayne: The 103R cartridge sees a resistive load of 1.6k. As moving coil cartridges are almost universally flat in their response it makes little sense to try & load it with a low resistance. The 1.6k is made up of 2ea, 802 ohm 1/4w metal foils that also provide the necessary ground reference needed for the mike per chips. At normal operating level there is no noise in my Orthodynamic headphones.

I decided to treat the mc cartridges like a microphone. I thought the Lehman Black Cube Phono Pre used a That 1510/1512 but a check of the unit says they are using a dual burr/brown/TI opamp. I guarantee mine sounds better.

Now working on a balanced 47k ohm input unit for moving magnet pick ups. Will likely use LME 49720's on each channel.

User avatar
mediatechnology
Posts: 3656
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Mar 06, 2019 10:16 am

Been there. Done that. viewtopic.php?f=7&t=753
I decided to treat the mc cartridges like a microphone.
We've been doing that since the beginning of this thread, the THAT1512 MC thread and the ZTX851 thread. JR since 1982 in Popular Electronics. For years. Welcome to the party. You're late.

I think you'll find that the LME49720 isn't all its cracked up to me as a MM preamp due to its noise current from bias-current-cancellation. viewtopic.php?f=6&t=423&p=8665&hilit=lme49720#p8665
The OPA1612 is similar in its inferior performance to the LME49720.

In the above case I blew off the LME49720 due to the difficulty of finding quiet ones without burst noise.
I am not alone in this as Victor M has found in his super low-distortion oscillator.

The LME477X0 also have a DECT 6.0 tuned circuit on each and every pad just waiting to pickup the nearest phone. Out-of-band signals make the LME49720 rectify. viewtopic.php?f=6&t=939

Use the LME49720 like a FET input amp with high DC circuit resistances and they can latch-up too: viewtopic.php?f=6&t=641

About the only bias-current-compensated dual that's worth considering is the dual OP27 the OP270 or OPA227.
I think you'll find that if you ignore the hype of the LME49720 and look at the lowly NJM2068DD (about 30 cents) it will be quieter than just about anything out there.
NJM found the sweet spot of Vnoise and Inoise.

Use a real cart as a source and the differences in noise due to Inoise are readily apparent.
https://ka-electronics.com

SOCIAL MEDIA PLATFORMS should advance FREEDOM OF SPEECH. Yet too many Americans have seen their accounts suspended, banned, or fraudulently reported for unclear “violations” of user policies.
No matter your views, if you suspect political bias caused such an action to be taken against you, share your story with President Trump.

White House Tech Censorship Reporting Link: https://whitehouse.typeform.com/to/Jti9QH

Post Reply